Journal Article Copepod community succession during warm season in Lagoon Notoro-ko, northeastern Hokkaido, Japan

Yoshizumi Nakagawa  ,  Hideaki Ichikawa  ,  Mitsuaki Kitamura  ,  Yasuto Nishino  ,  Akira Taniguchi

9 ( 2 )  , pp.249 - 257 , 2015-06
Lagoon Notoro-ko, located on the northeastern coast of Hokkaido, Japan, and connected to the Okhotsk Sea by a human-made channel, is strongly influenced by local hydrography, as water masses in the lagoon are seasonally influenced by the Soya Warm Current and the East Sakhalin Current. We here report on the succession of copepod communities during the warm season in relation to water mass exchange. Copepods were categorized into four seasonal communities (spring/early-summer, mid-summer, late-summer/fall, and early-winter) via a cluster analysis based on Bray–Curtis similarities. Spring/early-summer and early-winter communities were characterized by the temperate–boreal calanoid Pseudocalanus newmani, comprising 34.9%–77.6% of the total abundance of copepods during times of low temperature/salinity, as influenced by the prevailing East Sakhalin Current. Late-summer/fall communities were characterized by the neritic warm-water calanoid Paracalanus parvus s.l., comprising 63.9%–96.3% of the total abundance, as influenced by the Soya Warm Current. Mid-summer communities comprised approximately equal abundances of P. parvus, Eurytemora herdmani, Scolecithricella minor, and Centropages abdominalis (12.8%–28.2%); this community is transitional between those of the spring/early-summer and late-summer/fall. Copepod community succession in Lagoon Notoro-ko can be largely explained by seasonal changes in water masses.
北海道北東部の海跡湖能取湖の水塊は、沿岸域を流れる宗谷暖流と東樺太海流によって季節的に影響を受ける。我々は、能取湖の非結氷期における水塊交替に着目して、カイアシ類群集の遷移について報告する。カイアシ類群集は、Bray-Curtisの類似度指数によって4つの季節的な群集(春/初夏、夏、晩夏/秋および初冬群集)に分類された。春/初夏および夏群集では、Pseudocalanus newmani が東樺太海流の優占時期にカイアシ類群集中で優占した。晩夏/秋群集では、Paracalanus parvus s.l.が宗谷暖流の優占時期に優占した。夏群集では、P. parvus、Eurytemora herdmani、Scolecithricella minor およびCentropages abdominalis が春/初夏と晩夏/秋群集の移行期に等しく優占した。能取湖のカイアシ類群集の遷移は水塊の季節的交替によって説明することができる。

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